Koscielny stabbed home a flick-on from France team-mate Olivier Giroud in the 72nd minute at a rain-lashed Emirates Stadium and Leicester were held 0-0 by Bournemouth, with Riyad Mahrez squandering a penalty.

Manchester City, third, can close to within a point of Leicester if they win at Watford later on Saturday.

Meanwhile, Wayne Rooney scored as Manchester United ended an eight-game winless run by beating Swansea City 2-1. Arsenal were bidding to build on the 2-0 win over Bournemouth that had sent them top of the table, but Newcastle squandered several opportunities to go ahead.

Arsenal goalkeeper Petr Cech had to produce smart saves to thwart Giorginio Wijnaldum either side of half-time, while Aleksandar Mitrovic diverted a volleyed cross from Ayoze Perez over the bar from close range.

With the home fans growing restless, Koscielny supplied the breakthrough 18 minutes from time, sneaking in behind Perez to toe the ball past Rob Elliot after Giroud had got his head to a high ball. Leicester have now gone three league games without winning after their stalemate against 10-man Bournemouth at the King Power Stadium.

Jamie Vardy hit the post in the first half and was then fouled by Simon Francis in an incident that saw the Bournemouth defender sent off and yielded Leicester's 60th-minute penalty. But for once this season Mahrez's radar betrayed him, the Algerian's penalty parried by Bournemouth goalkeeper Artur Boruc.